Nearly a third of "test jurors" quizzed last week about the deadly 2012 Richmond Hill explosion had formed opinions about the three suspects or knew enough about the case from media coverage to make defense attorneys concerned about getting fair trials for their clients.

The question now for Marion Superior Judge Sheila A. Carlisle is whether that is enough to move the trials out of Marion County.

The use of a test jury was revealed Monday during the first day in a change of venue hearing for Mark Leonard.

Leonard, his half brother Bob Leonard, and Monserrate Shirley, Mark Leonard's former girlfriend, are charged with murder and 46 counts of arson and conspiracy to commit arson in the Nov. 10, 2012, blast that killed Shirley's next-door neighbors, John and Jennifer Longworth. The explosion also damaged more than 80 homes in the Southeastside subdivision and upended the lives of dozens of families.

All three defendants have asked Carlisle to move their trials out of Marion County. They contend they cannot get fair trials because of extensive publicity about the case. The hearing on Mark Leonard's request is expected to run all week.

Indianapolis attorney Jack Crawford, who has worked both as a prosecutor and defense counselor, said the use of a test jury is a unique approach.

"I don't know of it being done in Indiana," he said, "but it has been done in other high-profile cases across the country."

Larry Landis, executive director of the Indiana Public Defender Council, said the judge must determine whether the prospective jury pool has been so tainted by publicity that it will not be possible to find a fair and impartial jury.

Based on testimony in court Monday, about one in five of the 125 test jurors knew enough about the Richmond Hill case to be immediately disqualified. Most already had formed an opinion on the innocence or guilt of the suspects — most leaning toward guilt.

Nearly a third of the test jurors had raised concerns among defense attorneys that they might know too much about the case or have formed an opinion. Attorneys on Tuesday will further question about 20 more of those jurors.

Landis said there is "no clear, bright line or standard" for determining how much knowledge about a case is too much.

"That's a determination the judge will have to make," he explained.

The test jury was called only for informational purposes and will not hear the case when it does go to trial. The jurors did not know that when they were questioned Friday, Carlisle said in court. The judge said the jurors called back Tuesday will be informed they are part of a test.

The prospective jurors on Friday filled out standard jury questionnaires and special forms addressing issues related to the change of venue request, such as how much they knew about Mark Leonard and the Richmond Hill case and whether they had formed any opinions about the explosion.

Crawford said he thinks it was smart for Carlisle to use the test jury before calling "hundreds of prospective jurors" in an effort to find 12 jurors and several alternates for a trial.

In the end, Crawford added, he expects the change of venue request to be granted.

"The media coverage, here and nationally," he said, "has been just off the chart."

No trial dates have been set, but Mark Leonard is scheduled to be tried first.